1. Field of the Invention
The present invention relates to a throttle valve control apparatus which controls an amount of air flowing toward an engine, and more particularly to a throttle valve control apparatus of a so-called drive-by-wire type in which a throttle valve for controlling an opening area of an intake passage extending through a throttle body is driven by a motor operating in correspondence to an electric signal output from an ECU.
2. Conventional Art
A description will be given of a conventional throttle valve control apparatus with reference to FIG. 3. Reference numeral 1 denotes a throttle body, inside which an intake passage 2 is provided through. The intake passage 2 is controlled so as to be opened and closed by a throttle valve 4 which is attached to a throttle valve shaft 3 rotatably supported to the throttle body 1. The left end of the throttle valve shaft 3 in the drawing protrudes toward the left side from the throttle body 1, a throttle valve lever 5 is fixed to and arranged at the left end, and a spring force in a direction for closing the throttle valve 4 (this spring force is shown by a clockwise direction A in FIG. 2) is energized to the throttle valve shaft 3 by a throttle return spring 6. That is, the throttle return spring 6 is arranged in the outer periphery of the throttle valve shaft 3, one end thereof is engaged with the throttle body 1, and another end thereof is engaged with the throttle valve lever 5. Further, an opening degree sensor T and a motor M are arranged at the right end of the throttle valve shaft 3. The opening degree sensor T is structured such as to output an electric voltage, which is in proportion to a rotation angle of the throttle valve shaft 3, toward an ECU (not shown), and a groove of flat face TB of a sensor rotor TA constituting the opening degree sensor T is engaged with and arranged in a portion of flat face 3A formed at the right end of the throttle valve shaft 3, whereby the throttle valve shaft 3 and the opening degree sensor T are synchronously rotated. Further, the motor M is driven on the basis of an output signal from the ECU (not shown), a first gear 7A is fixed to and arranged on an output shaft MA of the motor M, a second gear 7B is fixed to and arranged near the right end of the throttle valve shaft 3, and the first gear 7A and the second gear 7B are engaged with each other, whereby a rotation of the motor M is transmitted to the throttle valve shaft 3. In accordance with the structure mentioned above, when the signal is output from the ECU toward the motor M, the motor M is rotated accordingly, and this rotation is transmitted to the throttle valve shaft 3 via the output shaft MA, the first gear 7A and the second gear 7B so as to rotate the throttle valve shaft 3, whereby the throttle valve 4 can control the opening of the intake passage 2 in correspondence to the output signal of the ECU. In the operation mentioned above, the motor M is rotated against a spring force of a throttle return spring 6 at a time when the throttle valve 4 is operated to be opened.
In accordance with the conventional throttle valve control apparatus mentioned above, the throttle valve shaft 3 and the opening degree sensor T are structured such that the portion of flat face 3A at the right end of the throttle valve shaft 3 is inserted and arranged within the groove of flat face TC of the sensor rotor TA in the opening degree sensor T and they are connected to be interlocked, whereby a hysteresis is generated at the opening operation time and the closing operation time due to a gap in the insertion portion, so that there is a risk that an accurate angle detection of the throttle valve shaft 3 is damaged. Further, in accordance with the gap mentioned above, a punching abrasion is generated at a long time use, and there is a risk that the gap is expanded and the detection capability is further reduced.
The present invention is made by taking the problem mentioned above into consideration, and an object of the present invention is to provide a throttle valve control apparatus which can stably detect an angle of a throttle valve shaft for a long time with no hysteresis in detecting an angle of the throttle valve shaft, and can make a motor for driving the throttle valve shaft compact.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided a throttle valve control apparatus in an internal combustion engine comprising:
a throttle valve which is mounted to a throttle valve shaft crossing over an intake passage provided in a throttle body so as to open and close the intake passage;
a motor which is arranged in one end of the throttle valve shaft via a gear and controls to open and close the throttle valve on the basis of an output signal from an ECU;
an opening degree sensor which is arranged so as to face to an end portion of the throttle valve shaft, detects a rotation angle of the throttle valve shaft, and outputs a rotation angle signal toward the ECU; and
a throttle return spring which energizes a force in a direction of closing the throttle valve with respect to the throttle valve shaft,
wherein a sensor rotor constituting the opening degree sensor is pressed and energized to an end portion of the throttle valve shaft in a rotation direction of the throttle valve, by a rotor return spring which energizes the sensor rotor in a direction for opening of the throttle valve.
In accordance with the throttle valve control apparatus of the present invention, the groove of flat face in the sensor rotor is always pressed toward the portion of flat face in the throttle valve shaft in the rotation direction thereof by the rotor return spring, and the groove of flat face and the portion of flat face are always kept in the pressed state. Accordingly, no hysteresis is generated in the output signal from the opening degree sensor in the direction of opening and closing for the throttle valve shaft, and no punching abrasion is generated between the groove of flat face and the portion of flat face at the long time use. Further, since the pressing direction of the spring force in the rotary return spring is set to be reverse to the pressing direction of the spring force in the throttle return spring, it is possible to reduce the relative spring force of the throttle return spring applied to the throttle valve shaft, whereby it is possible to employ a compact motor having a low rotational torque.